Test of cracking resistance of recycled aggregate concrete at early stage

The influence of the recycled coarse aggregate (RCA) replacement ratio, the amount of fly ash and slag powder on the cracking resistance of recycled aggregate concrete (RAC) during the early age was investigated by means of knife-edge binding method in this paper. The total cracking area in flat of 1 m2 was applied as the main indicator to evaluate the cracking resistance for specimens. The results show that the total cracking area of RAC decreases with the increase of RCA replacement ratio. When the RCA replacement ratio reaches 100%, the total cracking area of RAC is 1.5 times that of natural aggregate concrete (NAC). The fly ash can effectively improve the cracking resistance of RAC. Compared to the control group without mineral admixture, the total cracking area of RAC specimens with fly ash accounting for 30% of the binder decreases by 72.1%. The effect of restraining the cracking area with slag powder is weaker than that with fly ash. However, the slag powder can decrease the discreteness of crack distribution. © 2015, Science Press. All right reserved.